I did run CCleaner, MalwareBytes, and Spybot Search & Destroy which seem to have fixed the problem.

What had me fooled was the popup window was titled: "Mozilla - Firefox advertisement". Just because it said it was from them, does not make it so.

One additional question - After running Spybot Search & Destroy, I tried to delete the items found, but was told I could not because I was not an "administrator".
My account is setup as "administrator", but still will not work on removing the Spybot items.

You could also go Start - type spybot then right click on it to run as an admininstrator to see if that will do it, but I wouldn't enable the hidden admin account as you don't know what you are dealing with.

Also possible is to run a portable antimalware app like Windows Defender Offline (WDO). For a charge of $40.00 Hitman Pro (Cloud multi-vendor antimalware) can remove a lot of stuff, and it uses multiple antimalware engines. Just be careful not to remove anything which is rated by probability ratings instead of flagged outright. Same with MBAM run from Safe Mode or the Hidden Administrator Account or "Run As Admin" from the Desktop Icon Right-Click Menu.

In my Ubuntu Linux, the newest Firefox is faster than before and loads better, and it is still completely ad-free.